Thermal stability and electrical properties of BiFe1-xMxO3 (M=Al3+, Ga3+) ceramics

BiFeO3 (BFO) is a fascinating multiferroic material, exhibiting ferroelectric and G-type antiferromagnetic characteristics simultaneously. In this work, non-magnetic Al3+ and Ga3+ doped BFO (BFAO and BFGO) ceramics were synthesized via sol-gel and conventional sintering methods. Structural, thermal stability and electrical properties of samples were analyzed in detail. X-ray diffraction (XRD) patterns of powder and ceramic samples demonstrated efficient crystallization, consisting of rhombohedral structures with R3c space group for small amounts of added dopant. Thermal analysis exhibited that BFO decomposes into Bi25FeO39 and Bi2Fe4O9 at 950 degrees C. It is found that Al3+ and Ga3+ doping readily contribute to decomposition, as supported by calculations from first-principles. BiAlO3 and BiGaO3 are unstable and would spontaneously decompose, if they could be synthesized using ordinary technology. As a result, decomposition temperatures of doped powders decreased to 680 degrees C. Dielectric behavior can be explained through the Maxwell-Wanger model and Koop's theory. Dielectric loss decreased with increasing substitution. Leakage current density of doped ceramics became 2-3 orders of magnitude lower than that of BFO ceramic, improving performance and championing applications of modified BFO in future.